Formation, Preservation, and Metallogenic Fertility of Juvenile Crust in the Eastern Tethyan Collisional Orogens

Genesis and growth of continental crust is fundamental to maintain life and supply resources to our society. It is widely accepted that continental collision zones are favored locations of crustal preservation, yet it remains unclear when and how continental collision generates juvenile crust and maintains net crustal growth. Here we carry out hafnium isotopic mapping of three collisional orogens with distinct maturity in the Tethyan domain, i.e., the Zagros, Himalaya, and Qinling, to reveal evolution of juvenile crust in collisional zones. Our results indicate that the amount of juvenile crust generated and preserved in collisional orogens far exceeds previous estimates. The pre–collisional juvenile crust generated by arc magmatism was mostly preserved in Zagros, slightly reworked in Himalaya, and partly lost in the Qinling orogen. In growing orogens such as Zagros and Himalaya, the collision produces juvenile crust and leads to net crustal growth by input of juvenile mafic magmas derived from partial melting of both subduction–modified lithospheric mantle and asthenosphere. In decayed orogen such as Qinling, there is little juvenile crust produced during collision due to limited mantle melting. The juvenile lower crust is fertilized in ore–forming components, which can be released into hydrous felsic magmas during later remelting, and thus plays a significant role in the genesis of magmatic–hydrothermal ore deposits in collision zones.